問題描述:
某電商平臺,首發一款新品手機,每人限購2臺,預計會有10W的并發,在該情況下,如果扣減庫存,保證不會超賣
解決方案一
利用數據庫鎖機制,對記錄進行鎖定,再進行操作
SELECT?*?from?goods?where?ID?=1?for?update; UPDATE?goods?set?stock?=?stock?-?1;
利用排它鎖將并行轉化為串行操作,但該方案的性能和用戶體驗較差
解決方案二
使用setnx命令(在key不存在時,創建并設置value 返回1,key存在時,會反回0)來獲取鎖,在業務邏輯中,我們可以通過這樣的方案來操作
Jedis?client?=?jedisPool.getResource(); ????????while(client.setnx("lock",String.valueOf(System.currentTimeMillis()))?==?0){ ????????????Thread.sleep(10000); ????????} ????????//coding?here? ???????client.del("lock")
方案二進階
考慮到死鎖問題,即現成A獲取鎖后,宕機了,導致鎖一直無法釋放,我們可以通過get命令獲取鎖的時間戳,通過他進行超時判斷,并進行釋放
????Long?TIMEOUT_SECOUND?=?120000L; ????????Jedis?client?=?jedisPool.getResource(); ????????while(client.setnx("lock",String.valueOf(System.currentTimeMillis()))?==?0){ ????????????Long?lockTime?=?Long.valueOf(client.get("lock")); ????????????if?(lockTime!=null?&&?System.currentTimeMillis()?>?lockTime+TIMEOUT_SECOUND)?{ ????????????????client.del("lock"); ????????????} ????????????Thread.sleep(10000); ????????} ????????........................... ????????........................... ????????client.del("lock")
方案二加強
方案2的算法中,為了確保在非超時情況下,鎖只能由有鎖的線程進行釋放,可以在value的時間戳中,拼上線程特征碼
????Long?TIMEOUT_SECOUND?=?120000L; ????????String?featureCode?=?"machine01"; ????????Jedis?client?=?jedisPool.getResource(); ????????while(client.setnx("lock",featureCode+":"+String.valueOf(System.currentTimeMillis()))?==?0){ ????????????Long?lockTime?=?Long.valueOf(client.get("lock").substring(9)); ????????????if?(lockTime!=null?&&?System.currentTimeMillis()?>?lockTime+TIMEOUT_SECOUND)?{ ????????????????client.del("lock"); ????????????} ????????????Thread.sleep(10000); ????????} ????????........................... ????????........................... ????????if?(featureCode.equals(client.get("lock").substring(0,?8)))?{ ????????????client.del("lock"); ????????}
? 版權聲明
文章版權歸作者所有，未經允許請勿轉載。
THE END
